# Glossary

> Plain-English definitions of cold email and deliverability terms, from SPF and DKIM to inbox placement, warmup, and complaint rate.

Source: https://docs.ayinbox.com/learn/glossary/

A [#a]

ARF (Abuse Reporting Format) [#arf-abuse-reporting-format]

The standardised format mailbox providers use to report spam complaints back to senders. AY Inbox ingests ARF reports where available.

Alignment [#alignment]

The DMARC requirement that the authenticated domain (from SPF or DKIM) match the visible "From:" domain. Relaxed alignment matches at the organisational level; strict requires exact equality.

B [#b]

Bounce [#bounce]

A failed delivery. Hard bounces (invalid mailbox, blocked domain) suppress immediately. Soft bounces (mailbox full, temporary outage) are retried with backoff and suppressed if persistent.

BIMI [#bimi]

Brand Indicators for Message Identification. Lets you publish a verified logo that some clients display next to your messages. Requires DMARC `p=quarantine` or stricter, plus a VMC certificate for full display.

C [#c]

Cold email [#cold-email]

Unsolicited mail to a recipient with whom you have no prior relationship. Distinct from spam by intent: cold mail is targeted, relevant, and gives the recipient a real way to say no.

Complaint rate [#complaint-rate]

Percentage of delivered messages marked as spam by recipients. Google's bulk-sender threshold is 0.10%. Above 0.30% is in the danger zone.

D [#d]

DKIM [#dkim]

Cryptographic signature that proves a message was authorised by the domain's key holder and not modified in transit. See [SPF, DKIM and DMARC](/learn/spf-dkim-dmarc/).

DMARC [#dmarc]

The policy that ties SPF and DKIM to the visible From: domain and tells receivers what to do on failure. See [SPF, DKIM and DMARC](/learn/spf-dkim-dmarc/).

F [#f]

FBL (Feedback Loop) [#fbl-feedback-loop]

A direct channel from a mailbox provider that forwards spam-complaint events to the sender so they can suppress the recipient.

H [#h]

HMAC signature [#hmac-signature]

The cryptographic signature on a webhook delivery that lets you verify the call really came from AY Inbox and wasn't tampered with.

I [#i]

Inbox placement [#inbox-placement]

Share of accepted messages that land in the recipient's primary inbox (not spam, not promotions). The metric that actually matters. See [Inbox placement](/learn/inbox-placement/).

IP warmup [#ip-warmup]

Gradually increasing send volume from a new IP so receivers learn its behaviour. Required for dedicated IPs; not required for shared IPs you're sending through.

M [#m]

MTA (Mail Transfer Agent) [#mta-mail-transfer-agent]

The server that sends and routes mail. In cold-email tools, the "sending engine" is effectively the MTA.

O [#o]

OOO (Out of Office) [#ooo-out-of-office]

Auto-reply indicating the recipient is unavailable. AY Inbox classifies OOO replies and suppresses them from sequence engagement metrics.

P [#p]

Pool (warmup) [#pool-warmup]

A group of warmed mailboxes that send warmup mail to one another. Quality of the pool matters more than size. See [Warmup pools](/learn/warmup-pools/).

PTR (Reverse DNS) [#ptr-reverse-dns]

The DNS record that resolves an IP back to a hostname. Mailbox providers expect outbound mail to come from IPs with matching PTRs.

Q [#q]

Quarantine [#quarantine]

The state of a mailbox temporarily removed from the warmup pool and cold sending. Triggered by reputation warning thresholds.

R [#r]

Reply detection [#reply-detection]

Identifying a recipient's reply to a sent message, even when the reply chain has been forwarded or quoted text changes.

S [#s]

SPF [#spf]

DNS record listing the servers and services authorised to send mail for a domain. See [SPF, DKIM and DMARC](/learn/spf-dkim-dmarc/).

Suppression [#suppression]

Excluding a recipient from future sends. Triggered by hard bounce, complaint, unsubscribe, or manual addition.

T [#t]

TLS [#tls]

Transport-layer encryption used between mail servers (and between AY Inbox and your mailbox provider).

U [#u]

Unified inbox [#unified-inbox]

A single interface that shows replies across every connected mailbox in a workspace. See the [Unibox guide](/guides/unibox/).